David Cameron pleaded with Scotland not to rip apart the Union as he issued a warning that independence is a “leap into the dark” from which there is no going back.

The Prime Minister told voters “we desperately want you to stay” as he prepared to travel north to hit the campaign trail with Labour leader Ed Miliband and Deputy Prime Minister Nick Clegg.

In an article for the Daily Mail, the premier set out some of the UK’s greatest achievements, including the Scottish enlightenment, the abolition of slavery and defeating fascism, to highlight “what is at stake” on September 18.

The rest of the world “looks on with awe and envy” at the modern British achievements such as the National Health Service and state pension system, Mr Cameron added.

He wrote: “The United Kingdom is a precious and special country. That is what is at stake. So let no one in Scotland be in any doubt: we desperately want you to stay; we do not want this family of nations to be ripped apart.

“Across England, Northern Ireland and Wales, our fear over what we stand to lose is matched only by our passion for what can be achieved if we stay together.

“If we pull together, we can keep on building a better future for our children. We can make sure our destiny matches our history, because there really will be no second chances. If the UK breaks apart, it breaks apart for ever.”

Yesterday, former Labour prime minister Gordon Brown spoke movingly as he vowed to “nail the SNP lie” that Scotland's health service is at risk of privatisation.

Addressing activists in Glasgow, he said: “I love Scotland, I love the NHS.

“When my daughter died it was as the result of not being able to do anything to save her life, and my respect for the NHS grew as a result of the experience that Sarah and I had.”